In recent years liquid crystal panel display devices in which the RGBW system is adopted have been developed. With the RGBW system each pixel is made up of an ordinary red (R) subpixel, green (G) subpixel, and blue (B) subpixel, and a white (W) subpixel. Luminance is improved by the W subpixel, so the luminance of a lighting device, such as a backlight, which lights a liquid crystal panel from, for example, the rear can be reduced. This reduces the power consumption of an entire liquid crystal panel display device.
With the above display system, on the other hand, adjustment of the luminance of a lighting device made according to a change in displayed image may degrade display quality. Accordingly, if gradations of an image to be displayed differ between, for example, two successive frames, the following technique is proposed. A first dimming process for changing the luminance of a lighting device according to each gradation and a second dimming process for changing the level of gradation distribution setting according to each gradation are performed for a plural frame period (see, for example, Domestic Republication of PCT Publication No. 2012/017899).